These types of vehicle seats allow on the one hand a longitudinal adjustment on a longitudinal rail, and on the other hand, an adjustment between a seating position and a completely or partially folded forward functional position, which may be a cargo or easy entry position, for example.
For this purpose, the vehicle seat has a four-link configuration having four link parts and four hinge points which connect the link parts. An angled seat part and a backrest part, for example, are generally provided as link parts, the seat part being provided for accommodating a seat cushion, which may also be supported on the lower area of the backrest part. The backrest part may represent the entire backrest or a lower portion of the backrest. In these types of articulated structures, for example a lower receiving part, which is generally rigidly coupled to a front foot or which itself represents the front foot, and a coupling rocker between the receiving part and the backrest part, for example, are used as additional link parts.
In addition to its front foot, the vehicle seat is generally accommodated with a rear foot in the longitudinal rail, whereby, for example, the front foot may be lockable in the longitudinal positions. The rear foot is accommodated with a locking apparatus on the longitudinal rail, which may be unlocked for folding or pivoting forward.
The pivot motion from the seating position initially leads in a first upward partial path into a middle position, and is generally assisted by a compensation spring so that the user does not have to overcome the entire weight of the seat. This is followed by a further partial path into the functional position, which may occur completely or partially automatically, for example.
For this purpose, the compensation spring is provided between two parts of the four-link configuration, for example between the coupling rocker and a suitable location on the seat part, and is already tensioned in the seating position.
However, production-related tolerances in the individual components, in particular also the front foot and rear foot and their locking apparatuses, generally result in a certain play in the individual parts of the four-link configuration. In particular, the action of the compensation spring results in twisting of the link parts of the four-link configuration having tolerances. This may cause, for example, twisting of the feet in the longitudinal rail, in particular also tilting of the rear foot in the longitudinal rail, for example. Such tilting of the feet may result in interfering resistance during the longitudinal adjustment and in the sliding motion, and the seat may jerk and become jammed.